Streaming Caused by Oscillatory Flow in Peripheral Airways of Human Lung

Oscillatory flow facilitates gas exchange in human respiration system. In the presentstudy, both numerical calculation and PIV (Particle Image Velocimetry) measurementindicate that, under the application of HFOV (High Frequency OscillatoryVentilation), apparent steady streaming is caused and augmented in distal airways bythe continuous oscillation, i.e., the core air moves downwards and the peripheral airevacuates upwards within bronchioles. The net flow of steady streaming serves toovercome the lack of tidal volume in HFOV and delivers fresh air into deeper lungregion. Also, numerical calculations reveal that the intensity of steady streaming ismainly influenced by the geometry of airways with provided oscillatory frequencyand tidal volume, and it rises with Re and Wo up to a Re of about 124 and Wo ofabout 5. Steady streaming is considered as an important factor for the ventilation efficiencyof HFOV.